Some Physical Factors Influencing the Feeding Behavior of Daphnia Magna Straus

Abstract

The feeding behavior of Daphnia magna was studied in relation to the effect of animal size, water temperature, and light intensity. D. magna were fed on pure cultures of Chlorella vulgaris and Saccharomyces cerevisiae labelled with radioactive phosphorus.As size of D. magna increased over the range 1.25 mm to 3.54 mm, both maximum filtering rate and maximum feeding rate increased. The relation between the increase of filtering rate and the increase of maximum feeding rate is such that the "incipient limiting level" (the external level above which there is no limiting effect of food supply) also increases as size of Daphnia increases. The feeding rate of D. magna was studied over the temperature range 5 °C to 35 °C. The temperature optimum for feeding was approximately 24 °C.Feeding rate was also studied under conditions of total darkness and at light intensities of 100, 300, 500, 1,000, 3,000, and 10,000 ft-c. Illumination from total darkness to 1000 ft-c did not appear to affect the feeding rate of D. magna.The results of this investigation are discussed in relation to previous studies of filtering rates of other Crustacea.

Regulation of cladoceran filtering rates in nature by body size, food concentration, and diel feeding patterns1

“…The cause of the decrease in filtering rate is more complex than the simple clogging of a sieve; it involves regulation, such as alteration of thoracic appendage and mandibular movement as well as labral and postabdominal rejections (e.g. McMahon and Rigler 1963;Burns 19686). Therefore I examined the ingestion or feeding rate (f) response using the combined dry weight of the seston < 3 1 pm and the added yeast as an estimate of the available food.…”

“…hunger can cause temporary increases in the feeding rate of Daphnia (McMahon and Rigler 1963;Geller 1975), high nocturnal feeding rates might be explained as part of a daily hunger cycle. I examined possible hunger responses of Daphnia by measuring the frate changes in response to food additions made at brief intervals during the evening.…”

“…Daphnia that has been starved (Geller 1975) or prefed for 1 h below its maximum feeding rate (McMahon and Rigler 1963) exhibits unusually high feeding rates for 30 min or less and then returns to lower prefed maximum feeding rates. In the pond, a Daphnia population that quickly migrates toward the surface might be expected to arrive in a "hungry" state after many hours of filtering at low daytime rates near the bottom.…”

Free‐swimming Daphnia pulex can avoid following Stokes' law

“…Previous experiments have used acclimation times of 30 min (McMahon and Rigler 1962;Burns 1968) or 1 h (Dodson and Ramcharan 199 1) before observing Daphnia. We asked whether acclimation protocol was a factor influencing Daphnia swimming behavior.…”

“…Individuals were placed in a beaker with 1 x lo5 cells ml-l of Chlamydomonas in the videotaping room overnight to acclimate to the first temperature for at least 12 h. We chose a concentration of 1 x lo5 cells ml-l because this is at the incipient limiting level measured by McMahon (1965) for Daphnia magna similar in size to our D. pulex. This level is where algae ingestion was maximum and rejection was minimum; also, Daphnia has been shown to exhibit consistent unirritated swimming behavior at this food concentration (Dodson et al 1995).…”